U.S. Pat. No. 3,842,194 of Clemens discloses a video disc having a playback system utilizing variable capacitance. In one configuration of the Clemens system information representative of the recorded picture and sound is encoded in the form of a relief pattern in a relatively fine spiral groove on the surface of a disc record. For example, groove widths of about 2.7 micrometers and groove depths of about 0.5 micrometer may be used. During playback a pickup stylus about 2.0 micrometers wide having a thin conductive electrode thereon, for example, about 0.2 micrometer thick, engages the groove as the record is rotated by a supportive turntable. Capacitive variations between the stylus electrode and the record surface are sensed to recover the pre-recorded information.
In the system of the above type the use of a relatively fine record groove and the groove engaging requirements of the pickup stylus results in a stylus tip which is extremely small. In U.S. Pat. No. 4,162,510 of Keizer a novel keel tipped pickup stylus structure is disclosed. The pickup stylus is part of the signal pickup assembly of a video disc record player. The assembly is housed in a protective housing such as the pickup cartridge described in Leedom, U.S. Pat. No. 3,952,147 which also facilitates replacement of the signal pickup assembly without any critical manual adjustments or connections.
Dholakia, in U.S. Pat. No. 4,077,050 describes a leaf spring or flylead for urging the stylus into the record groove. One end of the leaf spring is secured to the stylus and the second end is mounted within the cartridge above the stylus. The flylead provides stylus tracking pressure, properly locates the free end of the stylus arm relative to the carriage and establishes electrical connection between the electrode on the stylus and the signal processing circuitry of the player.
The flyleads are thin, for example, about 0.0002 to about 0.0008 inch (5.08-20.32 micrometers) thick and about 0.04 inch (2.5 centimeters) long, and are generally fabricated out of an electrically conductive metal. Thin beryllium copper alloy sheets may be used to fabricate the flyleads. The sheets are fragile and cannot be easily handled because they readily bend and kink. Also difficulties have been encountered in using standard photolithographic methods to fabricate the flyleads. For example, undercutting of the photoresist layer during development and of the beryllium copper sheet during etching are sometimes observed.
A solution to these problems is disclosed in the copending application of Dinardo, Jr., Ser. No. 081,486, filed Oct. 3, 1979. In the Dinardo, Jr. application a method for preparing a flylead for a video disc playback cartridge is taught which comprises the steps of laminating a dry film photoresist to both sides of a thin metal sheet, exposing one side to light through a patterned mask, developing the patterned side with a solvent developer to selectively remove certain photoresist areas, etching the resulting exposed metal sheet portions and removing the remaining photoresist from both sides of the etched metal sheet.
Further developments in the manufacture of the cartridge assembly have resulted in the need for a flylead which may be semi-automatically assembled. For this purpose it is desirable to have a flylead having one portion of a surface coated with a pattern of solder. It would therefore be desirable to have a method for preparing a flylead for use with a semi-automatic assembly process.